Automatic toll collection systems (such as an Electric Toll Collection System, ETC) for toll roads and advanced cruise-assist highway systems (AHS) or smart cruise systems for automobiles traveling on roads have been developing as part of intelligent transport systems (ITS), road transport systems for the next generation.
The ETC is a system in which a toll is collected via radio communication between an automatic toll payment device (such as an IC card or a radio tag) mounted in an automobile and an automatic toll collection apparatus disposed at a tollgate, without stopping traffic on toll roads such as expressways. Implementation of the ETC is expected because the system not only facilitates toll payment but also has effects of mitigating traffic congestion, reducing personnel expenses, and the like.
In the ETC, a detection means such as radars of the automatic toll collection apparatus disposed at the tollgate detects that an automobile traveling on a road has approached the tollgate with a predetermined distance therebetween.
Subsequently, a radio communication device of the automatic toll collection apparatus transmits a signal to the traveling automobile and prompts the automatic toll payment device of the automobile to transmit, via radio communication, information (such as a type of vehicle, contract details, a paying account, and the like) which is necessary to determine a toll for the automobile. The automatic toll payment device of the automobile then transmits the information necessary to determine the toll for the automobile to the radio communication device of the automatic toll collection apparatus.
The automatic toll collection apparatus receives the information necessary to determine the toll for the automobile, calculates the toll based on a traveled distance of the automobile on the toll road, and executes a toll collection process.
Further, in the AHS, for example, a lane marker is provided at each of predetermined positions of a road along driving lanes for automobiles. A detector, such as a radar, of a cruise-assist device mounted in an automobile traveling on the road detects the position of the lane marker to detect an appropriate traveling route. In order to make the automobile travel on the appropriate traveling route, the driver of the automobile is warned of the possibility of deviation from the driving lane, or automatic intervention in the operation of a steering device of the automobile is performed for safe driving. Furthermore, various types of communications are carried out between communication equipment of the lane markers disposed on the road and the vehicle in order to determine the traveling route and improve transportation facilities.
Thus, in the above-described ETC and the AHS, which are part of the ITS, the traveling automobile is used as an object of communication, detection or measurement carried out by using electromagnetic waves of relatively high frequency. For this reason, the operation of communication, detection or measurement using electromagnetic waves of relatively high frequency needs to be carried out accurately the instant the traveling automobile passes through a predetermined place.
However, in the ETC or the AHS, unnecessary electromagnetic waves scatter due to the electromagnetic waves of relatively high frequency reflecting off the road or the like. The unnecessary scattered electromagnetic waves may be received by a receiver of the ETC or the AHS, which may cause errors in the operation of communication, detection or measurement.
Moreover, studies have been conducted in an attempt to shorten the term of construction and improve the quality of a pavement of a paved road by applying factory-prepared precast concrete to the pavement of road areas for the communication between stations of the ETC and automobiles, or the pavement of roads with lane markers for the AHS.
However, a conventional pavement with concrete slabs is formed of a material of high density and small porosity (so-called “dense and solid material”). Since this material has a dielectric constant larger than that of air, electromagnetic waves easily reflect off the surface of the concrete slab.
Moreover, because a large amount of electromagnetic waves reflect off the surface of the concrete slab, the electromagnetic waves cannot be transmitted to the inside of the concrete slab. For this reason, even with a pavement formed so as to absorb radio waves by mixing a dielectric material and a magnetic material into a concrete slab, a sufficient radio wave absorption effect cannot be obtained.
Further, when water accumulates on the surface of the concrete slab due to rain or the like, the amount of radio waves reflecting off the surface of the concrete slab becomes large.
Because of the aforementioned characteristics of the concrete slab, when the concrete slab is used to form the pavement of road areas for the communication between stations of the ETC and automobiles, or the pavement of roads with lane markers for the AHS, it is difficult for the pavement to efficiently absorb electromagnetic waves emitted from the system and suppress generation of unnecessary scattered electromagnetic waves.
In view of the above, in order to absorb electromagnetic waves and prevent generation of unnecessary scattered electromagnetic waves, a first object of the present invention is to provide a novel electromagnetic wave-absorbing pavement material having an electromagnetic wave absorption function. A second object of the present invention is to provide a novel pavement for a road constructed by using the electromagnetic wave-absorbing pavement material. A third object of the present invention is to provide a novel pavement in which a pavement slab formed with the electromagnetic wave-absorbing pavement material is used.